The present invention relates to determining a load weight of a vehicle. It finds particular application in conjunction with independent pneumatic circuits and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other applications.
A typical Trailer Roll Stability Program (TRSP) measures air pressure on an air suspension and converts the pressure reading to a load percentage, and even to an interpreted weight, based on a single pressure input, which is either integrated via a port on the TRSP valve or with an external electrically connected pressure sensor. Since air-bags in an air suspension are typically all pneumatically connected, the air pressure in any one air bag is representative of the pressure of the entire air bag circuit. The leveling or height control valve allows air in or out of the air suspension circuit based on the load placed on the suspension. A height control valve activates based on both vehicle empty sprung weight and payload added or removed to/from the vehicle. The pressure in any one air bag typically does not vary much from any other air bag in the system, which comes to equilibrium within a relatively short amount of time. The air bags along with electronic filtering act to give a stable signal from a pressure measurement perspective. From a TRSP perspective a single measurement is adequate to interpret the load on the trailer.
Some air suspension systems have multiple independently controlled pneumatic circuits that don't equilibrate to a single pressure. One example of such an independently controlled pneumatic system is a dual-circuit pneumatic system having independent circuits on respective sides of a vehicle. Other examples of such systems have independently controlled pneumatic circuits for respective vehicle axles or even individual air bags.
From a TRSP perspective, since pneumatic pressure in one of the circuits may not match the pneumatic pressure(s) in the other circuit(s), multi-circuit pneumatic circuits for air bag suspension control systems may be problematic. More specifically, there is not a single pneumatic pressure on which the load percentage or interpreted weight may be based.
The present invention provides a new and improved apparatus and method for determining a load weight.